A couple small updates.
1) When I pressed Niantic support about the fact that all of their recorded transactions mirrored mine except for the dates, the rep mentioned that receipt dates don't always match the purchase dates. I asked then how the receipts would be dated for more than a week before they claim the purchases happened. Haven't heard back, but I'll stay on them.
2) My Apple ID was disabled again today - twice in one week. I have no idea why, either. When I contacted Apple support, the rep just said it was related to the charges on my account I disputed. They stuck by that answer, despite the fact I had to get my account reactivated just 4 days ago for the same reason.
3) I did some digging, and it seems like the way that Apple/iTunes provides information to you about your purchases on your receipt does not include the same information they provide to merchants (in this thread https://developer.apple.com/forums/thread/68487). For security reasons, merchants are provided, from what I've gathered, an encrypted version of your purchase details. While this is good for a consumer security/privacy perspective, it also means it is very difficult for iTunes receipts to be matched with a specific transaction on the merchant's end. So, that's somewhat dissuaded me but I'm going to keep on Niantic Support and will probably reach out to Apple Support again and tell them about the situation and see if there is any info I could provide from my receipts that might help Niantic resolve the issue. I may also try to find some way to file a complain with BBB - it seems reckless for Apple to provide their users with a purchase receipt that is virtually useless when it comes to verifying and tracing transactions.
I'll keep updating on anything I find out. Again, even though I haven't had much luck, I feel like if these types of complaints reach both Niantic and Apple support more often, it would (hopefully) encourage one or both of them to take this issue a bit more seriously.